Humans Can't Resist Those Puppy-Dog Eyes

THURSDAY, April 16, 2015 (HealthDay News) -- When humans and their four-legged, furry best friends look into one another's eyes, there is biological evidence that their bond strengthens, researchers report.

Oxytocin -- the same hormone responsible for helping mothers bond to their infants -- increases in both dogs and their owners when they maintain eye contact, the Japanese scientists found.

"Certainly, people who suggest their dog is part of the family are probably quite right," said Dr. Greg Nelson, director of surgery and diagnostic imaging at Central Veterinary Associates in Valley Stream, N.Y. "A dog is not merely a housed animal that accepts food from us and tries to cohabitate. Rather, they have a relationship more as a parent and child or peer to peer."

In a series of experiments, the researchers showed that a positive "biofeedback loop" appears to exist between dogs and humans, whereby a rise in oxytocin in one triggers a rise in the hormone for the other.

The findings were published in the April 17 issue of the journal Science.

"Humans have evolved to use human-specific communicative tools, mainly the eye gaze," said study co-author Dr. Takefumi Kikusui, a veterinarian and researcher in the department of animal science and biotechnology at Azabu University in Kanagawa, Japan.

"Eye gaze may be functioning instead of physical touch or hugging. The point is that dogs can show the same communicative gazing toward humans," Kikusui said.

In the first experiment, dogs and their owners interacted for 30 minutes. Those who spent the most timing gazing into one another's eyes had higher concentrations of oxytocin in their urine afterward.

Dog-owner pairs without the lengthy eye gazing did not have the same increase in oxytocin. Owners also touched their dogs and spoke to their dogs more when they had more eye contact with them.

In the second experiment, researchers sprayed oxytocin into the nostrils of 27 dogs and released each into a room with their owner and two strangers. The female dogs spent more time looking at their owners, who also experienced an increase in oxytocin.